Two-way pulse multichannel system employing cathode-ray tube modulators



April 26, 1949- E. LABIN ETAL Two-WAY PULSE MULTICHANNEL SYSTEM EMPLOYING 'CATHODE-RAY TUBE MODULATORS Sheets-Sheet `1 Filed Aug. 24, 1946 vQN Sms@

ATTORNEY April 26, 17949. E. LABIN E'rAL L SYSTEM EMPLOYIN oDULAToRs TVIOWAY PULSE MULTICHANNE A CATHODE-RAY TUBE M Filed Aug. 24, 1946 2 Sheets-Sheet 2 A TTORNE' Y Patented Apr. 26, 1949 UNITE-D STATES PATENT OFFICE TWO-WAY PULSE MULTICHANNEL SYSTEM EMPLOYING CATHODE-RAY TUBE MODU- LATORS 3 claims.

This invention relates to multi-channel communication systems and more particularly to multi-channel systems employing multiplex modulators and demodulators or the cathode ray tube type.

In our co-pending applications, E. Labin-D. D. Grieg, Serial Nos. 565,152 led November 25, 1941i and 567,414 filed December 9, 1944, U. S. Patent No. 2,465,380, granted March 29, 1949, we have disclosed receiving and transmitting terminals respectively, for multiple channel communication systems. Such systems make use of a group or" pulses wherein each channel is represented Aby a pulse within a given spatial range in respect to a common marker pulse. pulses are modulated in phase or time in accordance with the intelligence to be transmitted wlthin the range in respect to the marker pulse. The pulses are derived from a single sinusoidal type base wave by means of a multiple channel modulating tube of the cathode ray type, and the intelligence is recovered from the respective pulses by a multiple channel demodulating tube, also of the cathode ray type. The respective terminals for transmitting and receiving, normally include in the case of the transmitter a base wave oscillator, a phaser, a multiple channel modulating cathode ray tube, and anoutput circuit leading to the transmitter; and in the case of the receiver include a width discrirninz'ltor for separating out the marker pulses, a base wave generator, a phaser, and a multiple channel demodulator cathode ray tube connecting to the variousA receiving channels.

It is an object of the present invention to provide a two-Way communication multiple channel system incorporating multiple modulator and demodulator cathode ray tubes at both terminals.

It is another vobject to provide a two-Way communication system of the typereferred to which employs a minimum number of base wave generators for the system as a whole.

It is a further object to provide in a system of the above type a two-way terminal for receiv ing and transmitting a plurality of multiple channels wherein a single base wave generator is employed both for the receiver and the transmitter.

In accordance with certain features and objects of the invention, we provide a two-way multiple channel receiving and transmitting system including at each terminal a transmitter and receiver. The system includes a stable koscillator at one terminal to provide the sweep potential for the multiple channel modulatorand demodu lator cathode ray tubes of such a terminal, the

The individual synchronizing channel being formed for instance, as one cf the channels of the transmitter or modulator tube. At the opposite terminal, the demodulator tube separates the signals of the different channels. A synchronizing channel selector is also provided to isolate the pulses of the synchronizing channel so as to control a generator which provides the sweep potential for the demodulating and modulating tubes of that termlnal. The return transmission circuit does not include a synchronizing channel since the oscillator of the first terminal controls the demodulating tube of that terminal. In accordance with certain other features of the invention, one to four base wave generators may be employed in this system, that is, one such generator may synchronize any one or more of the demodulator or modulator circuits oi the system as a whole. In order for the signals obtained from the return transmission terminal to be in phase with the original sweep controlling the modulating and demodulating tubes of the first or original terminal delay devices may be inserted at suitable points of the receiver circuit of the second terminal. f

These and other features and objects of the invention will become more apparent and the invention itself best understood upon consideration of the following detailed description of an embodiment of the invention 'to be read in connection with the accompanying drawings in which:

Fig. l illustrates partly in block and partly in diagrammatic form, a transmitting and receiving terminal in accordance with the invention, details of a multiple channel modulating tube circuitbeing shown;

Fig. 1A indicates in graphic form a typical group of pulses for multiple channel communication; and

Fig. I2 lshows partly in block and partly in diagrammatic form, the secondary terminal of the system, the multiple channel demodulating tube being shown in detail.

The terminal illustrated in Fig. 1 comprises a multiple channel de'modulaftor tube I which is of the cathode ray tube type, as described in detail in our above-defined co-pending application Serial No. 567,414 which produces and modulates a group of time modulated pulses in accordance with those shown in Fig. 1A. The tube l includes an electron gun assembly 2, the resulting electron beam being deected in a given pattern while passing intermediate a set of horizontal and ver tical deection plates 3. The electron beam is 3 made to traverse a circular path in respect to a target or anode assembly comprising an apertured barrier plate 4, a modulating system 5, a pulse time modulator plate 6, and a so-called dynode or secondary emission anode 1. The circular deflection of the beam with respect to the target assembly is obtained by means of two sinusoidal waves which are phased 90 with respect to one another and which are obtained from a base wave oscillator or generator 8 and a phaser ampliner circuit 9, connected to apply the phased voltages to the vertical and horizontal deflection plates 3. As described in greater detail in the aforementioned co-pending application, the' barrier plate 4 includes radially disposed apertures IU which serve to interrupt or chop up the electron beam as it travels past in a circle and passes therethrough toward the dynode target 1 between the modulating ele-` ments I I of the modulator system and through apertures I2 of the modulator plate 6. Each of the modulating elements II is connected to one` of the modulating signal channels I3 through a coupling transformer I4. The amplitude modulated signal voltage is applied through the transormers Iii to the deflecting portions II of the modulating system 5 to cause radial displacement of the electron beam to take place in accordance with the signal voltage at the elements II. The apertures I2 of the modulating plate 6 are shaped in such a mannerthat any radial displacement of the beam toward or away from the center of the circle described thereby results in a displacement in time of the pulse generated by the beam impinging on the dynode 1 in the output circuit indicated at I5.. On'e of the apertures l2 is shaped such as to produce a somewhat wider pulse which serves as a marker or a synchronizing impulse for each groupof pulses for any complete circular travel of the beam. A representative group of such pulses including a marker pulse is indicated in Fig. 1A, the marker pulse being indicated at I6 and intelligence carrying pulses I1 are Ishown to be variable in position, that is in tune, Within a given range, such range being xed as to relative distance from the marker pulse lfor ach of the respective channels. The time modulated pulses of the various channels are collected and applied to a cathode follower I8 and a transmitter circuit i9 for transmission to the opposite terminal. A receiver is shown in block form at 2D as connected to the output terminals of the phaser circuit 9 indicating the community of the base wave generator or oscillator 8 for both the transmitter and receiver of the terminal. Details of the receiver circuit 2l! will be described in connection with Fig. 2.

Referring now to Figure 2, the terminal illustrated therein comprises a receiver-detector circuit 2I which, after the pulses have been detected therein, feeds them into a width discriminator circuit 22 wherein the marker pulse is isolated and made to trigger a synchronizing base wave in a generator circuit 23. The base wave which is of a sinusoidal character is applied to a phase shifter 24 which serves to derive two sinusoidal waves 90 apart and which are applied -to the vertical and horizontal deection plates 25, respectively, to cause a circular deection of an electron beam produced in electron beam assembly 26 of a demodulator tube 21. The multiple channel demodulating tube, details of which have been described in the above-referred to Vapplica-- tion, Serial No. 565,152, also includes a barrier tained from the respective targets for the various circuits for the various channels.

plate .28 and secondary emission targets or dynodes 29 which are exposed to the action of the electron beam through suitable apertures in the barrier plate radially disposed adjacent the periphery thereof. The time modulated pulses, acting to key the electron beam on and off according to the leading and trailing edges of the pulses, are applied to one of the control grids 30 of the tube 21 from the receiver .2| and thereby cause an amplitude modulated signal to be obchannels according to the respective coincidence of the keyed beam with the respective targets. The envelope formed by the resulting amplitude modulated pulses is isolated in low pass filter circuits 3l leading to the respective audio output A transmitter circuit indicated at 32 is connected to be supplied with the time modulated multi-channel pulse group from a multi-channel modulator circuit 33 which receives `its controlling sweep voltage from the base wave generator 23 in the receiver circuit by way of a suitable delay circuit 34, and is modulated from associated signal channels. The transmitter circuit 32--33 is otherwise anal-` ogous to the one described in connection with Fig. l except that it does not include a synchronizing marker pulse channel because of the presence of the oscillator 8 which controls the modulator tube of the first-described terminal. The delay circuit 34 is added so as to maintain the synchronous relationship between the terminals which is otherwise disturbed due to the transmission time lag. The receiver 20 of the terminal illustrated in Fig. 1 is analogous to the receiver and demodulator circuits of Fig. 2 and may or may not include a delay line in preference to the delay line incorporated in the circuit of Fig. 2.

In operation, pulses modulated in time in accordance with the respective signals in the various channels I3 (Fig. 1) are emitted in the form of a pulse train by transmitter I9 including suitable marker or synchronizing pulses as indicated at I6 in Fig. 1A. As these trains of pulses are received and detected in the terminal shown in Fig. 2, the synchronizing pulses thereof are isolated in the discriminator circuit 22 and applied to the base wave generator 23 for triggering the same to generate a sinusoidal wave which serves to provide the deiiecting voltages for the circular path of the electron beam in the demodulator tube 21. The detected time modulated pulses are at fthe same time applied to the control grid 30 of the tube 21 to provide on and oir keying of the beam whereby amplitude modulated pulses are obtained in the output circuits of the targets 29 and the nnal audio signal in the respective circuits 3| as described in the above-mentioned application Serial No. 565,152. The base wave of the generator `23 obtained as a result of the marker pulse received also serves to synchronize the modulating tube circuit 33 of the transmitter 32, a delay in the phase of the wave being required. The transmitter circuit 32 shown in Fig. 2 and the receiver circuit 2n shown in Fig. 1 are also analogous to those described in detail in Figs. 1 and 2 respectively, except that only one original oscillator `has been shown in Fig. 1 which serves to provide the basic synchronization of the entire system. It is, however, contemplated fto' use oscillators for any one or all of the transmitters or receivers of the two terminals, instead of employing one oscillator or wave generator 8 as described. A separate wave generator or oscillator may also be employed for controlling each terminal. When that is the case, an oscillator located in the transmitter circuit 32 of the terminal described in Fig. 2 will be connected to both the multi-channel modulator circuit 33 and to the sweep circuit of the demodulator 21. In such a case, however, in order to synchronize the locally controlled sweep of the demodulator with Ithe pulses received from the other terminal, a variable delay device will be inserted between the oscillator of the modulator circuit and the demodulator in the second terminal. In the case of a base wave oscillator being used only in one terminal, it becomes unnecessary to provide in the return transmission for a synchronizing or marking pulse channel as will be understood by inspection.

It will be seen from the above that we have provided a two-way communication system which lends itself to synchronized control from one of the receiving or transmitting portions of either terminal and provides the possibility of using multi-channel modulating and demodulating cathode ray tubes in each of the two opposite terminals.

While the above is a description of the principles of this invention in connection with specic apparatus, it is to be clearly understood that this description is made only by Way of example and not as a limitation of the scope of this invention.

We claim:

1. In a. two-way system for communicating by means of multichannel trains of time modulated pulses, two two-way opposite terminals, means for transmitting multichannel time modulated pulse trains between both terminals along a given communication medium, each of said terminals including a multichannel pulse train modulator,

and a multichannel pulse train demodulator, and a common generator for producing control waves for said modulator and demodulator, the rst of said terminals including means responsive to the control wave for producing a synchronizing pulse interspaced between the multichannel signal pulses and transmitted along said communication medium, and the second ofl said terminals including means for separating said synchronizing rst terminal.

EMILE LABIN. DONALD D. GRIEG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,185,693 Mertz Jan. 2, 1940 2,265,216 Wolf Dec. 9, 1941 2,395,467 Deloraine Feb. 26, 1946 

